I have my interior out again and I keep looking at the plates for the rear seat seat belts. It looks like a strong, flat surface that would be a great candidate for a rear tower brace. I got the idea from looking at my friend's Nissan 350Z coupe. Just curious if anyone has tried anything like this?

 

Although i haven't tried it I think it could help improve stiffness along with other bracing. Let us know how it goes if you decide to try it.

 

How exactly does the car flex in that area and how would a strait bar connecting the two points help anything?

Much like connecting the shock mounts, this will only add weight with zero benefit

 

I was thinking of a bar there but to use as a harness anchor in the absence of any cage to mount to. Not sure of any stiffening benefit there.

 

I don't see any benefit, other then extra weight.

 

My thought too. There are bars for fourth and fifth gen Camaros that bolt to that area but the bar is used solely for harnesses. If you can weld just do a roll bar with a bar for a harness. Shouldn't cost more than $100